UCR issue-76: a new requirement for multiple CRSs?

Hello,

Discussion about UCR issue-70
<https://www.w3.org/2015/spatial/track/issues/70> led to the idea that we
might need an extra requirement for being able to work with geometry data
with multiple CRSs. We can use this thread to discuss if that is a good
idea. This new question is added to the tracker as issue-76
<https://www.w3.org/2015/spatial/track/issues/76>.

Different CRSs serve different purposes, so making geometric data available
with multiple CRSs is an existing practice. It seems to me that if such a
practice is already possible and there are no problems, then there little
need to make this an explicit requirement.

Are there examples where working with geometric data that have multiple
CRSs is problematic? Such examples could work well to justify making this
an explicit requirement. It could be that there are data formats or
software that do not support the concept of a spatial thing being modelled
by multiple geometries having different CRSs. In that case, it is really a
problem that needs to be solved.

Anyway, please speak your mind.

Regards,
Frans